The present invention relates to equipment calibration, and more particularly to calibration of semiconductor processing equipment having motor-driven shafts.
The manufacture of semiconductor substrates and devices typically requires many different types of semiconductor processing equipment for performing a variety of processing steps. The substrates and devices must be manufactured with extremely high levels of purity, uniformity and precision to ensure the desired chemical and structural properties are achieved. This requires accurate calibration of the semiconductor processing equipment to control the various parameters of the processing steps performed by the equipment.
Many types of semiconductor processing equipment including crystal growers, spin dryers, thin film deposition equipment, etching equipment, etc., apply motion to substrates or other materials during processing. In these types of equipment, values such as the speed and distance of motion become parameters which effect the result of the process. The motion is often imparted to the substrates or other materials by motors which drive a rotating shaft. Therefore, accurate measurement and calibration of the shaft rotation is necessary to control the process.
One method currently used to measure the rotation of the shaft includes visually monitoring a portion of the shaft while it is rotating, and counting the number of rotations during a selected time period. However, this method is limited to relatively slow speeds of a few hundred revolutions per minute (rpm). Since many motors are capable of driving a shaft at several thousand rpm, most of the range of these motors cannot be calibrated using this method.
Another method, used by military personnel to measure the rotation of military equipment such as motors, etc., involves connecting a rotary encoder to the shaft of the motor. In these military motors, at least one end of the shaft includes a tapered counter-sink adapted to receive a conical coupling. The conical coupling is attached to the rotary encoder and the coupling is pressed into the counter-sink and held in place by hand. The inward pressure on the coupling causes it to wedge in the counter-sink and grip the shaft. The rotation of the shaft is thereby imparted to the rotary encoder. One disadvantage of this method is that the user must hold the coupling in proper alignment with the counter-sink to ensure accurate reading. Furthermore, this method is not applicable to motors with shafts that do not include a tapered counter-sink.
The invention provides a system for measuring the rotational speed of a shaft driven by a motor. The system includes a rotation measurement device having a rotatable sensor and configured to generate a signal corresponding to rotation of the sensor. The rotation measurement device may be supported by a fixture mountable on the motor. A coupler is associated with the sensor and includes a gripping surface configured to contact and grip the end-surface of the shaft to couple the sensor to the shaft and impart the rotation of the shaft to the sensor. The system allows accurate calibration of a variety of different motion-dependent parameters for various semiconductor processing equipment.